I have a Nobile Infinity Split (waveboard). I am considering buying the Nobile Infinity FOIL Split (for Foiling AND waves).
Another option would be attaching my Alpine Foil to my current Infinit Split (waveboard). I know there are flex issues here. The solution would be to use a plate just like the Shinnster's (please see picture) when using the board on foiling mode.

I have a Nobile Infinity Split (waveboard). I am considering buying the Nobile Infinity FOIL Split (for Foiling AND waves).
Another option would be attaching my Alpine Foil to my current Infinit Split (waveboard). I know there are flex issues here. The solution would be to use a plate just like the Shinnster's (please see picture) when using the board on foiling mode.

What should I do? Thanks.

It is fairly easy to make a Shinnster-like plate for your existing board- lay wax paper over your board, then layup some carbon fiber over that (I’d say a few layers of uni-directional and a few layers of biaxial, along with some sort of core), if will cure into a shape that fits your board exactly. The only tricky part is adding inserts and getting them to line up, but it can be done with care.

You don’t need to vacuum bag it, mine was hand layup and has been holding up for ~100 sessions. I weighed it down with some books while curing. But if you have vacuum setup, it would be better.

I would not use the actual shinn plate as I think there is curvature to it so it may not fit your board.

As far as whether it is worth it, none of us can answer that, it is really up to you, and depends on how much you enjoy diy projects and how much you want to save some cash. I did a setup like this and it is heavy but otherwise fine. That said, I’m looking at switching to a designated foil board instead of trying to make a multi-purpose board work. Assuming you don’t have all the materials at home, expect to spend over $100 to get epoxy, carbon, stainless inserts, and core material. Also expect this to decrease the resale value of your board.